Recent Advances in Denitrogenative Reactions of Pyridotriazoles

Diazo compounds display versatile reactivity and therefore are widely used in organic synthesis. Diazo compounds bearing a 2-pyridyl or a related azine moiety on the diazo carbon exist in the form of fused 1,2,3-triazoles. In this short review, we summarize the recent advances in denitrogenative reactions of [1,2,3]triazolo[1,5- a ]pyridines ('pyridotriazoles') and related fused 1,2,3-triazoles. Over the past decade, there has been a surge of activity in this field, with novel denitrogenative reactions of pyridotriazoles induced by metal compounds, light, and Bronsted and Lewis acids having been devised. As a result, heterocyclic compounds and functionalized α-picolines as well as bio­active molecules have been synthesized. In the review, emphasis is also placed on the mechanisms of the new reactions. 1 Introduction 2 Ring-Chain Isomerization of Pyridotriazoles 3 Metal-Catalyzed Reactions 3.1 Rh(II) Catalysis 3.2 Rh(III) Catalysis 3.3 Cu Catalysis 3.4 Pd Catalysis 3.5 Catalysis by Other Metals 4 Metal-Free Reactions 5 Conclusion.